Method and apparatus for controlling the combustion of fuel in boiler furnaces



PEABODY June 22 1926.

E. H. METHOD AND APPARATUS FOR FUEL IN INVENTOR ERNEST H. PEABODY BY mamm- @fim ATTORNEY thus there is a greater pressure on the out- Patented June 22, 1926.-

UNITED STATES PATENT OFFICE.

ERNEST H. PEABODY, OF PELHAM MANOR, NEW YORK, ASSIGNOR TO PEABODY EN- GINEERING CORPORATION, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

MErrron AND APPARATUS FOR CONTROLLING THE COMBUSTION 0E EUEL 1N BOILER FURNACES.

Application filed July 14,

This invention relates to improvements in method and apparatus for controlling the combustion of fuel in boiler furnaces and more particularly for burning oil under forced draft and with high capacities.

In theexisting methods for burning oil, particularly those wherein very high capa cities are required, as for example in installations on board destroyers, battle-ships and the like, itis customary to enclose the steam generators in air-tight compartmen s into which air. is forced under pressure which may vary from two to eight inches watergauge. In these methods the casing of the boiler is obviously exposed to a considerable difference in air pressure between the outside and the inside, in other words a certain difference in draught pressures is required to force the air for combustion through the air registers of the oil-burning apparatus;

side of the air registers than on the inside, or in other words in the combustion chamber itself. Were it possible in practice to construct boiler casings which could be made and maintained absolutely air-tight, this method would give maximum boiler and furnace efficiencies. It is, however, not practicably possible to make and maintain a boiler casing air-tight, therefore the efficiency of this method of generating steam is injuriously affected by the infiltration and leakage of air from the'outside of the easing into the interior of the same. On the other hand it is obviously quite possible to enclose the air registers themselves in an air-tight easing into which the air may be directly discharged from the air supplying means, so that only that'part of the boiler casing immediately surrounding the air registers is subjected to the air pressure, and the major portion of the boiler casing, in fact the en tire portion which is subjected to air leakage, is subject only to the ordinary atmos- I pheric pressure. This is practicable for low capacities only.

However, with the high capacities required for installations on board destroyers, battle-ships and the like, there is certain to be a pressure existing inside the boiler casing or in the furnace higher than thatof the surrounding atmosphere. In other words, if the pressure produced by the air supplying means in the casing around the 1924. Serial No. 726,040.

air registers is limited only to that amount" which will create merely a pressure within the furnace equal to that of the surrounding atmosphere, the rate of combustion of the fuel will be limited, and the high capacities necessary will not be obtainable. Up to the limitations indicated this method of combustion is practicable, and is, in fact frequently used.

It is obvious that if a pressure exists within the furnace higher than that of the sur rounding atmosphere or the pressure outside the boilercasing, hot gases will be forced outward from the furnace. through small openings in the casing, so that the action will be reversed, namely, instead of cold air leaking into'the furnace, hot gases will leak outward into the boiler room. By thus preventing all leakage of air into the inside of the boiler, the efficiency of the generation of steam isgreatly improved, but this improvement is accompanied by a defeet even more serious than that of the loss in efficiency, namely, that the hot gases cause the casing to expand and distort, and the small leakage ordinarily existing is increased in quantity, a limit being soon reached at which the casing may actually be seriously damaged.

This method also has the additional objection that the gases passing into the boiler room are detrimentalto the health and comfort of the operating staff, and in fact these objections are sufficient to make the use of this method of discharging air merely into a double front or casing surrounding the air registersimp'ossible to use, except for very low capacities as previously stated. Thus,

on one hand we have leakage of air inward through the casing giving poor economy, and on' the other, insu'perable objections, al-

though the boiler economy is very greatly 1 improved.

My 'nvention consists in the combination of these two methods whereby I not only secure the high efficiency which is attained when there is no leakage of air inwardly through the boiler casing, but at the same time to prevent the objectionable features of blowing hot gases outward under the conditions which attend the use of the separate casing around the air registers.

This object can be obtained by combining two different air pressures, one of which,

namely the higher pressure necessary, to force the air through the registers, is limited to the neighborhood of the air registers themselves, whilst the other and lower pressure surrounds the boiler casing, and is adjusted in such a way that it will at all times equal or balance the pressure of the gases within the boiler casing. By thus balancing the two pressures, the hot gases are prevented-from being blown outward, whilst at the same time cold air is prevented from being forced inward. Thus, for example. assume that a pressure A is required in the immediate vicinity of the air registers to force the necessary air through same to give the desired rate ofcombustion, a pressure B lower than A will exist within the boiler furnace, and this pressure B Will vary according to the rate of combustion and the amount of pressure A required for same. In other words the difference between A and B represents the frictional loss through the air registers at the various rates of combustion. In order to secure the advantages of my method, therefore, it is only necessary to create an atmosphere around the boiler casing equal in' pressure to the pressure B.

A further object of my invention is to provide a method and apparatus for the automatic control of the air pressure inside and outside the furnace.

The foregoing and other features of my invention will now be described in connection with the accompanying drawing forming part of this specification in which I have diagrammatically represented an apparatus for the carrying out of my method, after which I shall point out more particularly in the claims those features which I believe to be new and of my own invention.

Referring to the drawings:

Figure 1 is a diagrammatical longitudinal .section of a boiler-room.

Figure 2 is a diagrammatical cross section of a boiler room on the lines 22, Figure 1.

Figure 3 is a diagrammatical cross section of a. boiler room, similar to that shown in Figure 2 embodying a modification which I employ.

In the carrying out of my invention I employ a closed air-tight compartment 1, a boiler 2 inside the compartment, a blower 3 outside the compartment, and an air duct 4 delivering air into a closed casing 5 on the boiler front 6. One or more burners 7 are enclosed within the casing 5 and the air from the blower is discharged into said casmg under pressure, enabling the burners to be operated at high power. The gases are discharged to the chimney through the uptake 8.

In a wall 10 of the furnace 9, I provide aswinging door 11 attached to the hinge 12 so that it can swing in or out under the influence of a balance of air pressure between the compartment 1- andthe'furnace 9. To this'plate is rigidly attached a lever or arm 13 pivotally connected to the rod 14, at-- tached to the bell crank 15 and arranged to move the rod or link 16 which is pivotally attached to a bell crank 17 which is connected to rod 18 which in turn is pivotally attached to arm 19 rigidly attached to damper 20. Rod 18 is variable in length by means of a turn buckle whereby the relative positions of dampers 11 and 20 may be adjusted. The damper ismmmted to open and close the opening 21 in the side of the air duct 4.

The modus operandi is as follows:

The blower 3 is operated at a speed suiticient to provide the necessary air for com bustion for the burners at the desired air pressure, said air pressure frequently being equal to 5" to 8" water pressure in high forced draft service. This air entering the furnace 9 through the air registers of the burners creates a plenum in the boiler furnace 9 which would cause the door 11 to swing outwardly toward the compartment 1 lifting the rod 14 and rotating the damper 20 in such a way as to allow air to pass from duct 4 through the opening 21 into the compartment 1.

The pressure of air in compartment 1 will at once be raised to the same pressure as that in the boiler furnace 9. Immediately this balance of pressure is reached, plate 11 swings back to its normal vertical position and the damper 20 is partly closed restricting the amount of air blowing from duct 4 into compartment 1. Let the pressure in the boiler furnace 9 fall below the pressure in compartment 1 and plate 11 will be moved inwardly towards the furnace and will, through the connections shown, completely close the damper 20 preventing air from flowing from the 'duct 4 into compartment 1. This will again balance the pressure and plate 11 will return to normal position.

.It will be understood that the exact position of plate 11, whether directly vertical or slightly to one side or other will depend upon the actual working conditions. The boiler being in operation there is a flow of gases fromthe furnace through the tube nests and the uptake 8, with a corresponding drop in pressure from the furnace to the uptake. Therefore, another method of applying the same principle would be to build a jacket casing around the entire exposed surface of the boiler, and to divide this casing into various compartments so that in each compartment the pressure of the air would balance the pressure inside the corresponding portion of the boiler casing. This method is illustrated in Figure 3 which illustrates a casing 50 built around the tube bank in which it is desired to maintain a pressure which balances the pressure in the tube bank. The tube bank wall 51 is provided with a damper 52 leading into the casing this damper is connected to damper 5 3 in the airduct by means of the connections 54 so that when the pressure in, the tube bank exceeds the pressure in its casing the damper 52 will'open, thereby opening the damper 53.

In this way a pressure B in the furnace will be balanced by means of the damper and connections shown in Figure 2 while the pressure C in the tube bank will be balanced by means of the damper and connection shown in Figure 3.

Although I have described in the fore going the invention with reference to oil burning apparatus, I wish it to be under stood that the invention is not-restricted-to this kind of fuel, but can be applied to any kind of furnaces burning liqu d, solid or gaseous fuel. y r It is obvious that many detail changes may be made without in any way departing from'the spirit of the invention which is to be regarded as limited only by the scope of the appended claims.- i a I claim as my invention: r

1. A method of controlling the combustion of-fuel to boiler furnaces whi eh comprises delivering air under pressure tosaid furnace, and controlling the air pressure in a, zone surroundingsaid furnace by the pressure within the furnace, so that the pressures will be substantially equalized.

2. A method ofcontrolling the combustion of fuel in a boiler furnace which comrises delivering air under pressure to said urnace and varying the pressure in a zone surrounding said furnace in accordance with the pressure within the same, so that the pressures will be substantially equalized. T

3. Apparatus for controlling the combustion of fuel in boiler furnaces which comprises a closed chamber surrounding said furnace, means for supplying air underpressure to said furnace, and means for maintaining substantiall the same pressure in said chamber as wit in the furnace.

4. Apparatus forcontrolling the combustion of fuel in boiler furnaces which comrises a closed chamber surrounding said urnace, means for supplying air under pressure to said furnace, and means for autowall.

matically maintaining substantially thesame pressure in said chamber as within the furnace.

5. Apparatus for controlling the combustion of fuel in boiler furnaces which comprises a closed chamber surrounding said furnace, means for supplying air under pressure to said furnace, and means controlled by the air pressure within the furnace for maintaining substantially the same pressure within the chamber, as in the furnace.

6. Apparatus for controlling the combustion of fuel in boiler furnaces which comprises a closed chamber surrounding said furnace, an air duct passing through said chamber and supplying air under pressure tq,the furnace, and means for. automatically admitting air from said duct into the chamber to maintain a desired pressure therein.

7. A paratus for controlling the combustiono fuel in boiler furnaces which comprises a closed chamber surrounding said furnace, an air duct passing through said chamber and supplying air under pressure to the furnace, and means controlled by the pressure within the furnace for admitting air from said duct into the chamber to maintain a desired pressure therein.

8. Apparatus for controlling the combustion of fuel in boiler furnaces which comprises a closed chamber surrounding said furnace, an air duct passing through said chamber and supplying air under'pressure to the furnace, an opening from said duct into the chamber, a damper for said opening, and means controlled by the pressure within the furnace for operating said damper to maintain a desired pressure within said chamber.

9. Ap aratus for controlling the combustion of el in boiler furnaces which comrises a closed chamber surrounding said urnace, an air duct passing through said chamber and supplying 'air under pressure to the furnace,,an opening from said duct into the chamber, a damper for the opening, an opening in the furnace wall, a damper therein, and means for controlling the movement of the damper in the air duct by the movement of the damper in the furnace Signed at New York in the county of New York and State of New York this 2nd day of July A. D. 1924.

' ERNEST H. PEABODY. 

